Steel alloy



Patented Jan. 27, 1942 UNITED STATES PATENT OFFICE James H. Taylor, Detroit, Mich., assignor to Gotham Tool Company, a corporation of Michlgan No Drawing. Application January 24, 1935, Serial No. 3,268

4 Claims. (Cl. 75-120) I Per cent Molybdenum 8.50 Chromium 4.00 Cobal 4.25 to 4.40 Tungsten 1.50 Vanadium 1.50 Carbon ..n 1.00 Boron 1.00

Another practicable formula employs the first five elements above enumerated in the same proportions, with Per cent Carbon .60 Boron .75

tive proportions,when combined with the indicated percentages of iron (with the usual commercial content of other substances) produces a surprisingly high quality of steel appropriate for cutting-tools, dies and the like, in which the tendency to decarburization is remarkably reduc'ed, the resistance to oxidation is increased, the degree of hardness is very high, and the cutting qualities and durability are considerably improved as compared with like alloys omitting the boron constituent. Thedescribed products are extremely satisfactory in forging and working.

My observation and tests demonstrate that typical alloys of iron and molybdenum and carbon, may be materially improved if a part of the normal carbon content is replaced by boron in approximately the illustrative proportions indicated.

tion, it is noteworthy that the'incorporation of boron in the alloy materially reduces the tendency, usually typical of molybdenum steels, toward undesirable decarburization. It has been attempted, with some success, to combat that tendency by coating molybdenum steels with borax during fabrication and heat treatment, the borax coating serving to protect the metal more or less from the oxygen of the air. This borax coating process, however, is expensive and inconvenient; and it is rendered superfluous when, according to this' invention, the proper proportions of boron are incorporated in the molybdenum steel alloys.

I. am not prepared to assert definite reasons for the superiorities of the product resulting from the practice of this invention, but I am inclined,

theoretically at least, to attribute the superior qualities, in part, to the supposition that the boron forms borides with other metals in the alloy, and that carbon and boron form a carbide of extreme hardness; the hardening of the matrix is perhaps attributable to grain refinement and change in space lattice on quenching the alloy from high temperature, and is accompanied by a certain amountof age hardening that occurs on heat treatment of alloys comprising sufiicient proportions of molybdenum or tungsten or both. The resistance of my alloys to decarburization and oxidation is probably, but not certainly, due to the formation of thin, impervious coatings of oxides of boron and the other constituent metals which tend to exclude the oxygen of the air.

As willbe evident to those skilled in the art, it is not essential to my invention that the precise proportions given in the illustrative formulae be employed or that the exact ingredients be used in all cases. On the contrary, my invention is susceptible of application to a considerable range of equivalents withinthe scope of the subjoined claims.

A form of boron usable, for example, in the aboveeformulaev is boron carbide, whichis approximately 80% boron and 20% carbon Among other advantages observable in tool steels produced in accordance with this inven- Iclaim: 1. An alloy steel comprising the following essential elements: carbon about 5% to .8570,

bility against the formation of soft skin at forging'and heat treating temperatures in ordinary atmospheres.

2. An alloy steel comprising the following essential elements: carbon not more than 1%,

formation of soft skin at heat treating temperatures in ordinary atmospheres.

3. An alloy steel containing carbon from 35% to 1.00%, molybdenum 8.50%, and boron in an amount not exceeding 1.00%, said steel being characterized by its resistance to decarburization at elevated temperatures in ordinary atmospheres.

an amount between about .75% and about 1.00%,

said steel having high speed properties and being characterized by its resistance to decarburization at heat treating temperatures in ordinary atmospheres.

JAMES H. TAYLOR. 

